US7737401B2 - Radiation measurement using multiple parameters - Google Patents
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- US7737401B2 US7737401B2 US11/820,488 US82048807A US7737401B2 US 7737401 B2 US7737401 B2 US 7737401B2 US 82048807 A US82048807 A US 82048807A US 7737401 B2 US7737401 B2 US 7737401B2
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- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
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- G01T1/02—Dosimeters
- G01T1/023—Scintillation dose-rate meters
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- United States Homeland security requirements set forth a need for devices capable of sensitive detection of gamma rays originating from hidden radioactive material (e.g. ANSI N42.32, IEC 62401).
- Conventional technology includes commercial grade radiation detectors that are sensitive enough to easily detect small increases in the intensity of a gamma radiation field, which could be of interest regarding the detection of hidden radioactive sources.
- radiation detectors are configured as portable devices that measure a so-called dose rate, which is a measure of the biological impact of the current radiation field.
- a time integration of the dose rate yields the accumulated dose value, which is of significant interest for the user of the radiation measurement device.
- dose rate can be measures as absorbed dose rate (Gray/hour); ambient dose equivalent rate (Sv/hour), exposure rate (R/hour).
- dose rate measures as absorbed dose rate (Gray/hour); ambient dose equivalent rate (Sv/hour), exposure rate (R/hour).
- Sv/hour ambient dose equivalent rate
- R/hour exposure rate
- gamma or “gamma radiation” is used for any photon radiation above 5 keV (gamma and X-ray radiation).
- the highly sensitive detector which is required for the detection of very small amounts of radiation
- the useful measuring range with respect to the dose rate is very limited. Due to saturation above certain gamma count values, these devices are not able to measure radiation at significantly higher levels that are hazardous to a person exposed to such radiation.
- the highly sensitive, low-level radiation detector device as discussed above, other types of commercial radiation devices are able to accurately measure levels of radiation well above a background level.
- such devices typically are not sensitive enough to accurately measure a presence of hidden radioactive material, which is known to be present based on a presence of radiation near or just above a natural background radiation level.
- One of two such radiation detector systems in the single portable device can be configured to detect radiation at a range just above natural radiation background level, but cannot be configured to measure the dose rate at higher levels of radiation.
- Another of the two different radiation detector systems can be configured to measure radiation well above the natural background radiation level, but cannot be configured to detect the lower levels of radiation.
- embodiments herein include an improved radiation detection device for measuring a broad range of radiation levels based on, for example, gamma count information representing radiation detected at different energy levels as well as a radiation intensity indicator value representing or reflecting an amount of overall radiation energy detected in the radiation sample.
- the radiation intensity indicator value is a value representing a relative amount of power or current required to maintain a photomultiplier tube at a constant voltage.
- a scintillator device absorbs gamma energy and coverts it into photons or light pulses.
- the photomultiplier tube converts the light pulses received from the scintillator into electronic pulses. Based on a combination of parameters such as the gamma count information and the radiation intensity indicator value, a processor calculates a radiation dose rate associated with the received radiation sample.
- radiation count information e.g., gamma count information
- gamma count information is only by way of example and that embodiments herein support detection of other types of radiation as well.
- Embodiments of the present invention are based on the observation that gamma radiation detected by “inorganic” scintillation (i.e., radiation detection) material, such as Thallium doped sodium iodide generates different pulse height distribution depending on received gamma energy.
- a radiation dose rate can be derived from the measured pulse height distribution as long as both the energy and dose rate dependency is known for the specific detector arrangement.
- a pulse height analysis e.g., analysis of the amount of radiation present at each of different energy levels
- a radiation detection device can calculate a radiation dose rate based upon gamma counts (i.e., radiation count information) produced by a plurality of counters that measure different levels of radiation energy as monitored by a detector.
- gamma counts i.e., radiation count information
- gamma counters i.e., radiation counter devices
- a scintillator can be used to convert received radiation into light pulses that, in turn, are converted into countable electronic signals at different energy levels via a photomultiplier tube.
- An amplifier is used to amplify the signals form the photomultiplier tube into more usable voltage levels.
- an amplifier that produces the electronic pulses from the photomultiplier tube may not be fast enough to create two distinct electronic pulses for two corresponding light pulses generated by the scintillator.
- two light pulses produced by the scintillator may only be converted into a single pulse that is counted via the counter devices. Accordingly, the counters may not actually reflect an amount of gamma rays or energy present in a radiation sample.
- Embodiments herein solve these and other problems.
- a parameter such as the measured current through a photomultiplier tube indicating an overall detected radiation level is used at least in part to calculate a radiation dose rate.
- a measurement of the count rates is combined with the measurement of the integrated light output in order to correct for the above mentioned energy dependence in respect to the dose rate calculation.
- One way to measure an overall level of light pulses or photons produced by a respective scintillator is to measure the power or current consumption information of the photomultiplier tube. As more photons are converted into electronic pulses by the photomultiplier tube, more current or power must be provided to the photomultiplier tube. Via application of an appropriate calibration factor to the power consumption information, techniques herein extend an upper limit of a radiation measuring range by several orders of magnitude than would be possible via use of count values alone.
- a radiation detection device as described herein can include a relatively small sized inorganic scintillator to convert received radiation into light pulses.
- the radiation detection device also can include a photo detector device (e.g., a photomultiplier tube) and amplifier to convert the light pulses received from the scintillator into electronic signals counted by a set of counter devices.
- a set of counter devices associated with the radiation detection device measures the levels of the light pulses and, thus, effectively measures the presence of radiation at different energy levels for low radiation levels in which the amplifier does not become saturated.
- a controller associated with the radiation detection device calculates a radiation dose rate value based on a combination of the counts of one radiation at one or more different energy levels as well as an amount of power (and/or current) consumed by the photo detector device (e.g., photomultiplier tube) to convert the light pulses into the counted electronic signals.
- embodiments herein include one or more radiation detector devices (e.g., a computerized devices, workstations, handheld or laptop computers) to carry out and/or support any or all of the method operations disclosed herein.
- a radiation detection device can include a controller or processor programmed and/or configured to operate as explained herein to carry out different embodiments of the invention.
- One such embodiment comprises a computer program product that has a computer-readable medium including computer program logic encoded thereon that, when performed in a radiation detection device having a processor and corresponding memory, programs the processor to perform the operations disclosed herein.
- Such arrangements are typically provided as software, code and/or other data (e.g., data structures) arranged or encoded on a computer readable medium such as an optical medium (e.g., CD-ROM), floppy or hard disk or other a medium such as firmware or microcode in one or more ROM or RAM or PROM chips or as an Application Specific Integrated Circuit (ASIC).
- the software or firmware or other such configurations can be installed onto a computerized device to cause the computerized device to perform the techniques explained herein.
- one particular embodiment of the present disclosure is directed to a computer program product that includes a computer readable medium having instructions stored thereon for supporting operations such as detecting broad levels of radiation.
- the instructions when carried out by a processor of a respective computer device, cause the processor to: i) receive gamma count information (i.e., radiation count information) representing counts for different energy levels of radiation in a radiation monitored radiation field; ii) receive a radiation intensity indicator value that is proportional to an amount of overall radiation energy detected in the radiation sample; and iii) based on a combination of the gamma count information (i.e., radiation count information) and the radiation intensity indicator value, calculating a radiation dose rate associated with the received radiation sample.
- gamma count information i.e., radiation count information
- the radiation intensity indicator value i.e., radiation dose rate associated with the received radiation sample.
- system, method, apparatus, etc. as described herein can be embodied strictly as a software program, as a hybrid of software and hardware, or as hardware alone such as within a processor, or within an operating system or a within a software application.
- Example embodiments of the invention may be implemented within products and/or software applications such as those manufactured by Thermo Fisher Scientific, Inc. of Waltham, Mass.
- FIG. 1 is an example block diagram of a radiation environment and measurement device according to embodiments herein.
- FIG. 2 is an example block diagram of a radiation measurement device according to embodiments herein.
- FIG. 3 is an example graph illustrating count rate versus radiation dose rate according to embodiments herein.
- FIG. 4 is an example graph illustrating a function to produce a dose rate based on a combination of radiation count information and a radiation intensity indicator according to embodiments herein.
- FIG. 5 is an example diagram of a flowchart illustrating a technique of measuring radiation according to embodiments herein.
- FIG. 6 is an example diagram of a flowchart illustrating more specific techniques of measuring radiation dose rates according to embodiments herein.
- a radiation detection device measures a broad range of radiation levels based on, for example, use of gamma count information representing counts for one or more different energy levels of radiation in a radiation sample (e.g., a monitored radiation field) as well as a radiation intensity indicator value (e.g., power or current consumption information indicating how much energy is required to maintain a photomultiplier tube at a constant voltage) that is proportional to an amount of overall radiation energy (e.g., light energy produced by a scintillator device that converts radiation into light pulses) detected in the radiation sample.
- a controller associated with a corresponding radiation detection device can calculate a radiation dose rate associated with the received radiation sample.
- an example radiation measurement device as described herein offers a convenient, simple and fast method to measure a broad range of gamma radiation via use of a portable device such as a pocket size, low power instrument.
- the radiation measuring instrument uses an “inorganic” scintillation (i.e., radiation detection) material, such as Thallium doped sodium iodide (e.g., NaI(Tl)) material, which operates in relatively compact or small sizes (e.g., a cylindrical shape with area of 1 to 10 ccm) to detect radiation.
- an “inorganic” scintillation (i.e., radiation detection) material such as Thallium doped sodium iodide (e.g., NaI(Tl)) material, which operates in relatively compact or small sizes (e.g., a cylindrical shape with area of 1 to 10 ccm) to detect radiation.
- FIG. 1 is a block diagram illustrating a radiation detection device 102 operating in environment 100 according to embodiments herein.
- the radiation detection device 102 includes a detector 115 (e.g., a scintillator that converts radioactive energy into light pulses), a photo-detector 120 (e.g., a photomultiplier tube), processor 113 (e.g., a digital signal processor), memory 112 , user interface 119 (e.g., a keypad, etc.), and display screen 130 .
- a detector 115 e.g., a scintillator that converts radioactive energy into light pulses
- a photo-detector 120 e.g., a photomultiplier tube
- processor 113 e.g., a digital signal processor
- memory 112 e.g., a keypad, etc.
- user interface 119 e.g., a keypad, etc.
- radiation source 105 emits a radiation field such as gamma rays that strike detector 115 .
- Detector 115 e.g., a scintillator
- Photons e.g., light
- At least a portion of the light emitted by detector 115 strikes photo-detector 120 .
- photo-detector 120 detects at least a portion of photons emitted by detector 115 .
- Processor 113 monitors one or more parameters associated with the detector/photo-detector 115 to determine a dose rate associated with a monitored radiation field such as that produced by radiation source 105 .
- processor 113 can receive radiation count information 107 as well as an overall radiation intensity indicator 108 associated with photo-detector 120 .
- radiation count information 107 indicates a number of light pulses (and thus radiation events) produced at each of multiple different energy thresholds (e.g., radiation thresholds).
- Overall radiation intensity indicator 108 can represent or be proportional a value proportional to an intensity of the light or photons received from photo-detector 120 regardless of the associated individual energy levels. In other words, a large number of small light pulses or a small number of large light pulses can yield the same value for the overall radiation intensity indicator 108 .
- Radiation measurement function 140 executed by processor 113 utilizes the received radiation count information 107 and overall radiation intensity indicator 108 to produce a radiation dose rate measurement
- An example of an embodiment for discriminating different light pulses to produce the radiation count information 107 (e.g., radiation count values at different energy threshold values) and a way of producing the overall radiation intensity indicator 108 is more particularly discussed in FIG. 2 .
- FIG. 2 is an example diagram illustrating radiation detection device 102 according to embodiments herein.
- radiation detection device 102 includes a detector 115 , photo-detector 120 , power supply 210 , amplifier 125 , comparators 142 (e.g., comparator 142 - 1 , comparator 142 - 2 , comparator 142 - 3 , . . . ), counters 144 (e.g., counter 144 - 1 , counter 144 - 2 , counter 144 - 3 , . . . ), counter 145 , memory 112 , processor 113 , user interface 119 , and display screen 130 .
- comparators 142 e.g., comparator 142 - 1 , comparator 142 - 2 , comparator 142 - 3 , . . .
- counters 144 e.g., counter 144 - 1 , counter 144 - 2 , counter 144 - 3 , .
- detector 115 e.g., a scintillator device absorbs high-energy radiation (from source 105 ) and emits corresponding photons that are, in turn, detected by photo-detector 120 .
- the number of photons emitted by detector 115 depends on the level of energy absorbed by detector 115 .
- photo-detector 120 Based on the photons striking photo-detector 120 , photo-detector 120 (e.g., a photomultiplier tube) generates an electrical signal 109 to drive the input of amplifier 125 . For example, a higher number of photons associated with a radiation event produce higher pulse amplitude of electrical signals 209 passed to the amplifier 125 .
- Detector 115 can be made from “inorganic” scintillation (i.e., radiation detection) material such as Thallium doped sodium iodide NaI(Tl) material. This type of material facilitates conversion of gamma energy into light energy in a manner as discussed above.
- a benefit of using NaI(Tl) in detector 115 is that the detector 115 can be configured into a relatively compact form using this material. As previously discussed, the detector 115 operates to convert gamma energy into (visible or invisible) light energy.
- detector 115 can include other types of scintillation material such as Cesium Iodide (CsI) to convert gamma energy into photons.
- CsI Cesium Iodide
- photo-detector 120 is a photo-multiplier tube, which receives light emitted by detector 115 and electrically couples to amplifier 125 .
- the photo-multiplier tube operates to receive an optical signal from the detector 115 (e.g., as caused by interaction of radiation with the NaI(Tl) material of detector 115 as previously discussed), generate an electrical signal or electrical pulses proportional to the light signal (e.g., proportional to the intensity of the light signal), and transmit the output pulses to the amplifier 125 .
- the amplifier 125 such as a linear amplifier, can be configured to adjust the pulse amplitude levels of respective output pulses to enable a discrimination of different pulse amplitude levels (corresponding to different radiation energy levels) via use of comparators 142 .
- Counters 144 driven by comparators 142 measure a presence of radiation at different discrete energy levels. Higher count values indicate presence of higher levels of radiation.
- the radiation detection device 102 utilizes one or more comparators 142 , each having a given threshold or threshold range, to achieve energy discrimination of the detected gamma radiation.
- Typical values correspond to gamma energies at one or more discrete threshold values in a range such as between 1 and 3000 kilo-electron Volts.
- Each comparator 142 includes a corresponding counter 144 (e.g., pulse counter) to detect a number of radiation events in a given comparator range. Accordingly, via respective counters 144 - 1 , 144 - 2 , and 144 - 3 , the processor 113 keeps track of the count rates for different threshold energy ranges.
- processor 113 can analyze levels of radiation emitted by radiation source 105 and provide an indication of the energy deviation ratio to a user and/or other devices. For example, in one arrangement as shown, processor 113 drives display screen 130 to provide an indication of a level of detected gamma radiation. In other embodiments, the processor 113 additionally or alternatively drives an audio device (e.g., a speaker), vibrator, and/or LED, etc. to warn when a respective energy deviation ratio reaches a dangerous or pre-determined threshold value.
- an audio device e.g., a speaker
- counter 145 can be a value representing an overall radiation intensity of light (and therefore radiation) over a spectrum, rather than the individual number of pulses in a specific energy range as do counters 144 .
- count C can vary depending on the total light intensity in the scintillator (e.g., intensity of light as produced by the scintillator as a result of exposure to a corresponding radiation field).
- power supply 210 provides power to photo-detector 120 .
- photo-detector 120 is a photomultiplier tube
- power supply 210 operates to maintain the photo-detector 120 at a constant voltage such as 800 volts.
- Power supply 210 can include a battery and a DC-DC converter that produces the constant voltage applied to the photo-detector 120 .
- power supply 210 can provide information (e.g., photomultiplier tube anode current information associated with photo-detector 120 ) via encoding and transmission of signal 211 to counter 145 (e.g., or register).
- signal 211 is proportional to an amount of photomultiplier tube anode current required by photo-detector 120 .
- signal 211 can be an oscillating signal or pulse rate (associated with a DC-DC converter in the power supply 210 ), whose frequency varies depending on how many photons are detected by the photo-detector 120 .
- Use of the pulse rate (as opposed to other current or power measuring techniques), eliminates the need for extra circuitry (e.g., an analog-to-digital converter, amplifier, etc.) otherwise needed to measure power or current associated with the photo-detector 120 .
- signal 211 is a higher frequency value (or includes a higher density of countable pulses) when photo-detector 120 converts a higher number of photons into electrical signal 209 used to drive amplifier 125 .
- signal 211 is a lower frequency value (or includes a lower density of countable pulses) when photo-detector 120 converts fewer photons into electrical signal 209 used to drive amplifier 125 .
- Counter 145 produces and stores a count value C, which varies depending on a number of oscillations associated with signal 211 .
- signal 211 is set to a proportionally higher frequency when more photons are detected by photo-detector 120 .
- counter C represents an overall radiation intensity indicator 108 associated with light or photons detected by photo-detector 120 because the value of counter C varies depending on how many photons are detected by photo-detector 120 .
- photo-detector 120 can include any of one or more additional photo detector devices that produce a measurable value representative of the number of photons produced by detector 115 . As mentioned above, such a device need not discriminate amongst energy levels, as this function is provided by amplifier 125 , comparators 142 , and counters 144 .
- processor 113 utilizes count values (e.g., count C 1 , count C 2 , count C 3 , and count C) to produce a radiation dose rate value (indicative of an amount of gamma radiation emitted by radiation source 105 ) for display on display screen 130 .
- count values e.g., count C 1 , count C 2 , count C 3 , and count C
- a radiation dose rate value indicator of an amount of gamma radiation emitted by radiation source 105
- energy analysis circuitry 228 includes comparators 142 and counter 144 .
- the radiation detection device 102 utilizes at least two comparators 142 , each having a given threshold (or threshold range), to achieve energy discrimination of radiation received from source 105 .
- Typical example values for a 3 threshold arrangement such as that provided by comparator 142 - 1 , comparator 142 - 2 and comparator 142 - 3 correspond to photon energies above 30 keV, above 200 keV and above 500 keV.
- comparator 142 - 1 enables a measurement of energy above 30 keV
- comparator 142 - 2 enables a measurement of energy above 200 keV
- comparator 142 - 3 enables a measurement of energy above 500 keV.
- Each comparator 142 includes a corresponding counter (e.g., pulse counter) 144 to count a number of radiation events within a given range or above a threshold value.
- Processor 113 electrically couples to the counters 144 and is configured to receive count rates read from the counters 144 .
- C 1 , C 2 , and C 3 are the count rates read out from the respective counters 144 - 1 , 144 - 2 , 144 - 3 , such as every second or in smaller intervals, for each energy threshold level (e.g., C 1 is for counts of particles impacting the scintillators in the greater than 30 KeV energy band, C 2 is for counts of particles impacting the scintillators in the greater than 200 KeV energy band, and C 3 is for counts of particles impacting the scintillators in the greater than 500 KeV energy band).
- the processor 113 is a microcontroller device having a corresponding arithmetic logic unit, and a corresponding storage representative for storing code and data.
- the microcontroller can include additional resources such as counters 144 and/or comparators 142 .
- a dead time correction formula can be applied to the measured count rates C 1 , C 2 , C 3 , etc.
- the values of a, b, c, . . . , n are weighing factors for each energy level threshold such as, for example, 2, 25, 50, 100, 200, associated with each corresponding one of counters 144 .
- a derived dose rate value can be filtered by a digital RC-filter or sliding mean value filter implemented by processor 113 .
- a value of the calibration factor, K(count) depends on the material and size of the crystal and the units (e.g., Gy/h, Sv/h, R/h or Rem/h) in which the dose rate is supposed to be expressed.
- count rates of up to 1 million counts per second (or slightly above) can be measured using counters 144 .
- Generation of pulses (e.g., from photo-detector 120 ) above this value generally cannot be measured accurately for reasons as discussed below.
- FIG. 3 A graph of count rates and corresponding dose rate calculations according to embodiments herein is shown in FIG. 3 .
- the dose rate values (mSv/h) as given in the figure and discussed in the text are given as example and refer to a certain gamma energy and detector arrangement, e.g. detector size and amplifier dead time.
- graph 300 provides a way to convert radiation count information 107 (e.g., count C 1 , count C 2 , count C 3 , etc.) into a corresponding dose rate. This conversion is captured in the Dose Rate(count) equation above.
- either the graph 300 or DoseRate(count) equation can be used to generate a radiation dose rate value below about 7 to 10 mSv/h.
- count values C 1 , C 2 , and C 3 by themselves cannot be used to derive a radiation dose rate above about 7 to 10 mSv/h.
- the ambiguity in graph 300 arises because the pulses produced by the photo-detector 120 overlap with each other above a certain radiation dose rate value of 7 to 10 mSv/h.
- saturation e.g., greater than about 1,000,000 counts per second
- the counters C 1 , C 2 , and C 3 do not properly represent or count the occurrence of radiation at each of the different radiation energy levels such as because the amplifier 125 is too slow.
- the peak count rates may appear at 10 mSv/h, but start to decrease at higher dose rates as well. This produces an ambiguity. For example, suppose count C 3 was measured as 10,000 counts per second. The corresponding dose rate could be either 0.2 mSv/h or 40 mSv/h according to the graph 300 . These represent substantially different amounts of radiation.
- Embodiments herein involve use of count value C (e.g., an overall radiation intensity indicator 108 as discussed above) as well as radiation count information 107 (e.g., the count values at different energy levels) to produce a radiation dose rate value.
- count value C e.g., an overall radiation intensity indicator 108 as discussed above
- radiation count information 107 e.g., the count values at different energy levels
- the radiation intensity indicator 108 does not experience saturation problems as do count values C 1 , C 2 , and C 3 when the amplifier 125 and/or photo-detector 120 (e.g., photomultiplier tube) becomes saturated.
- the radiation intensity indicator 108 may not properly produce an accurate radiation dose rate.
- embodiments herein include utilizing the overall radiation intensity indicator 108 (e.g., count C, which provides an indication when saturation occurs) as well as use the individual counter values at different energy threshold values (even though they do not reflect an actual number of radiation events) to produce a radiation dose rate.
- embodiments herein include an equation and/or look-up table to convert a combination of different received parameters (e.g., the overall radiation intensity indicator 108 and/or radiation count information 107 ) into a radiation dose rate value associated with a radiation sample.
- a combination of count rates C 1 , C 2 , C 3 and count rate C are used to determine the average gamma energy (e.g., radiation dose rate) in a broad radiation dose rate range including higher dose rate ranges where saturation occurs.
- count values C 1 , C 2 , and C 3 can be used to apply an appropriate calibration factor to count value C to produce an accurate radiation dose rate value.
- the count values C 1 , C 2 , and C 3 are still valuable for calculating a radiation dose rate.
- the count values C 1 , C 2 , and C 3 do not accurately reflect a number of radiation events above a peak count value as in graph 300 , they at least provide a relative indication of the gamma energy associated with the events being detected. For this reason, a combination of the radiation count information 107 and the overall radiation intensity indicator 108 (e.g., intensity of light energy produced by scintillator detector 115 ) can be used to accurately derive an actual radiation dose rate value.
- a high voltage applied to the photo-detector 120 can be generated by an arrangement of blocking oscillator type converters.
- a controller associated with power supply 210 includes a corresponding resource (e.g., a transistor driver) that controls a switching transistor in power supply 210 via application of rectangular-shaped pulses having a constant width.
- a corresponding resource e.g., a transistor driver
- the controller increases application of pulses to the switching transistor to increase an amount of power or current supplied to keep the voltage of the photo-detector at a constant voltage value.
- the amount of switching is proportional to a number of photons detected by photo-detector 120 .
- a presence of more pulses indicates a greater amount of light detected by the photomultiplier tube, while fewer pulses indicate a lesser amount of light in the photomultiplier tube.
- the count value C does not experience inaccuracy issues as do the counters C 1 , C 2 , and C 3 as a result of saturation.
- a frequency of these pulses that is necessary to maintain the high voltage is represented by the count rate C and is a monotonic function of the radiation intensity for a given gamma energy.
- the dose rate may not be accurately derived from C if the corresponding gamma energy associated with the monitored radiation field is not known.
- the same value C is achieved for a dose rate of 10 mSv/h (1 Rem/h) of 100 keV radiation as for a dose rate of approximately 50 mSv/h (5 Rem/h) of 1 MeV radiation. It is therefore beneficial to use the radiation count information 107 (e.g., count rates C 1 , C 2 , C 3 ) in order to correct the dose rate calculation based on the current measurement represented by C.
- W(C 1 , C 2 , C 3 , C) Weighing factor function for correction of the gamma energy dependence of the current to dose rate dependence.
- K(current) a calibration factor, whose value depends on specifications of the radiation detection device 102
- FIG. 4 is a graph 400 illustrating how different parameters (e.g., radiation count information 107 and overall radiation intensity indicator 108 ) can be used to calculate a radiation dose rate according to embodiments herein. For example, below a radiation dose rate of about 5 mSv/hour, a radiation dose rate can be determined largely based on radiation count information 107 as represented by line A. Above this threshold value, a combination of radiation count information 107 as represented by line A and overall radiation intensity indicator 108 as represented by line B can be used to calculate a radiation dose rate. Line C represents a calculated radiation dose rate using contribution from both radiation count information 107 and overall radiation intensity indicator 108 .
- parameters e.g., radiation count information 107 and overall radiation intensity indicator 108
- processor 113 can be configured to provide an indication of the energy deviation ratio and/or measured radiation dose rate to a user via display screen 130 or other sensory device.
- processor 113 can be configured to drive display screen 130 and display a calculated radiation dose rate in numerical form.
- the processor 113 can be configured to drive other devices such as one or more light emitting diodes (LEDs), sound generators, and/or vibrators to warn a user when the energy deviation ratio reaches a particular threshold value.
- LEDs light emitting diodes
- sound generators sound generators
- vibrators to warn a user when the energy deviation ratio reaches a particular threshold value.
- the radiation detection device 102 is configured as a computerized device (e.g., radiation detection device 102 includes one or more processors).
- radiation detection device 102 includes processor 113 .
- Memory 112 e.g., a computer readable medium
- a respective repository can store an application, logic instructions and/or respective data (associated with radiation measurement function 140 ) that are executed or utilized by processor 113 to carry out calibration and radiation measurements according to techniques discussed herein.
- Memory 112 can be of any type of volatile or non-volatile memory or, alternatively, storage system such as a computer memory (e.g., random access memory (RAM), read only memory (ROM), or another type of memory), disk memory, such as hard disk, floppy disk, optical disk, etc. Accordingly, one embodiment herein includes a computer-readable medium encoded with the functional instructions associated with radiation measurement function 140 .
- RAM random access memory
- ROM read only memory
- disk memory such as hard disk, floppy disk, optical disk, etc.
- one embodiment herein includes a computer-readable medium encoded with the functional instructions associated with radiation measurement function 140 .
- the processor 113 can be any type of circuitry or processing device such as a central processing unit, computer, controller, application specific integrated circuit, programmable gate array, or other circuitry that can access the radiation measuring application encoded within the memory 112 in order to run, execute, interpret, operate, or otherwise perform the radiation measuring application logic instructions. In other words, in one embodiment, processor 113 executes an application or code stored in memory 112 to carry out techniques as discussed herein.
- radiation detection device 102 Functionality supported by radiation detection device 102 and, more particularly, functionality associated with radiation measurement function 140 will now be discussed via flowcharts in FIGS. 5 and 6 .
- the radiation detection device 102 (or corresponding sub-components) generally performs steps in the flowcharts.
- FIG. 5 is a flowchart 500 illustrating a technique of producing a radiation measurement value according to embodiments herein. Note that flowchart 500 of FIG. 5 and corresponding text below will make reference to matter previously discussed with respect to FIGS. 1-4 .
- processor 113 in the radiation detection device 102 receives gamma count information 107 representing counts for different energy levels of radiation in a monitored radiation field.
- processor 113 receives a radiation intensity indicator value 108 (e.g., count C) that is proportional to an amount of overall radiation energy detected in the radiation sample.
- the count C can be a value proportional to a relative number of photons detected by photo-detector 120 .
- processor 113 calculates a radiation dose rate associated with the monitored radiation field based on a combination of the (gamma) radiation count information 107 and the radiation intensity indicator value 108 .
- FIG. 6 is a flowchart 600 illustrating a technique of measuring a radiation dose rate associated with a monitored radiation field according to embodiments herein. Note that flowchart 600 of FIG. 6 and corresponding text below will make reference to matter previously discussed with respect to FIGS. 1-5 .
- step 610 the detector 115 converts a monitored radiation field into light pulses.
- counters 144 (e.g., counters 144 - 1 , 144 - 2 , and 144 - 3 ) count the light pulses produced by detector 115 at different energy levels to produce (gamma) radiation count information 107 .
- counter 145 stores a radiation intensity indicator 108 value representing an overall amount of light energy or photons produced as a result of converting the monitored radiation field into the light pulses.
- processor 113 receives the (gamma) radiation count information 107 representing counts for different energy levels of radiation in a monitored radiation field such as that produced by radiation source 105 .
- step 625 the processor 113 receives the radiation intensity indicator value 108 from counter 145 .
- the processor 113 calculates the radiation dose rate based at least in part on the radiation intensity indicator value 108 and radiation count information 107 (e.g., amounts of respective gamma radiation count values for amounts of radiation detected at each of one or more different energy levels).
- step 635 based on a combination of the (gamma) radiation count information 107 (e.g., count C 1 , count C 2 , and count C 3 ) and the radiation intensity indicator value 108 (e.g., count C), the processor 113 calculates a radiation dose rate associated with the monitored radiation field using the equation or graphs as discussed above.
- the (gamma) radiation count information 107 e.g., count C 1 , count C 2 , and count C 3
- the radiation intensity indicator value 108 e.g., count C
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Abstract
Description
DoseRate(count)=K(count)*(a*C1+b*C2+c*C3 . . . +n*Cn).
DoseRate(current)=W(C1,C2,C3,C)*K(current)*(C−C(0))=Dose rate as derived from current measurement taking the pulse height distribution into account
W(C1,C2,C3,C)=0.15+(C−C(0))/C(0)*(C2+10*C3)/C1,
-
- where C(0): measured rate C at 4 mSv/h for Cs-137 and
- where K(current): Calibration factor in order to achieve the true dose rate at 70 mSv/h for Cs-137.
Claims (22)
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Cited By (2)
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Cited By (3)
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US20100302533A1 (en) * | 2007-11-15 | 2010-12-02 | Georg Fehrenbacher | Local Dosimeter for Measuring the Ambient Equivalent Dose of Photon Radiation, and Reading Method |
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US20080315110A1 (en) | 2008-12-25 |
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